Lufthansa has cancelled more than 500 flights today in anticipation of a five-hour strike by ground staff at German airports.
The German carrier warned it would cancel almost all short-haul and domestic flights, including services to and from the UK.
However, Lufthansa said it expected to operate long-haul flights on time.
Services to and from Frankfurt, Munich, Dusseldorf, Berlin, Hamburg and Cologne are affected.
The airline has cancelled flights throughout the day, including from London, Manchester, Birmingham and Aberdeen, despite the union action being expected to finish at noon.
Lufthansa advised passengers to check the status of their flight online before beginning their journey.
It said affected passengers would be rebooked or refunded without charge.
The strike by 33,000 members of the Verdi union is over a pay claim. The union has demanded a 5.2% wage increase.
Lufthansa has sought a pay freeze and demanded employees work an additional hour per week.